defroster problems

After i replaced my heater core everything comes out of the defroster in the top of the dash i have no vent or high low. I pulled off the defroster panel and all of the vaccume lines were hooked up so i pulled off the glove box and they all looked good so i dont know what could of went wrong, also it doesnt blow very good at all just a little air i just think it should blow a lot harder thanks for any advice.

Founding Member

Look up into the intake where the blower motor takes in air from inside the car. I think its on the passenger side in the stangs. My Dads T-bird sucked up a plastic bag and would not hardly blow any air, took us a good while to find that. I would use my hand vacuum pump to test the system for leaks as a whole, then narrow it down if you find any. you can get a little pump for $32 or so. It has a guage on it so you can see the leak, and comes with some good instructions to boot. You can pull the vac. line on the engine side of the firewall and pull a vacuum on the stuff in the car. If it holds, no leaks. Maybe a mechanical failure in an actuator or something. Or possibly a mechanical failure of the diversion door itself. Could take some exploring, thats why you go for the simple vac. leak route first.

Founding Member

On my 85 when I had defrost only I had a bad vacuum line in the engine compartment. It ran across the firewall over to the passenger side to a connector. Then it ran inside the passenger compartment to the heater controls. It was easy to find.

ok so where does this line in the engine compartment go to in the heater? i have one by the heater core hoses that is sitting there and i havent touched it but i knew it had to go to somthing but i didnt know what it went to also it isnt very long any other ideas where it goes to in the interior?

Founding Member

My hose had a hole in it just before the connector, between the connector and the other end where it attached to the vacuum tree if I remember correctly. When I replaced the hose then all of my heat and cool positions worked again.